mirrors/i2pd
2
0
Fork 0
mirror of https://github.com/PurpleI2P/i2pd synced 2024-11-10 00:00:29 +03:00
Code Issues Packages Projects Releases Wiki Activity

g^x mod p using precalculated table

Browse Source
This commit is contained in:
orignal 2016-04-09 22:44:13 -04:00
parent c45aab7cef
commit ffc666eaaa
1 changed files with 39 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
Crypto.cpp
View File

@ -153,32 +153,62 @@ namespace crypto
#define elgp GetCryptoConstants ().elgp
#define elgg GetCryptoConstants ().elgg
void PrecalculateElggTable (BIGNUM * table[][256], int len) // table is len's array of array of 256 bignums
void PrecalculateElggTable (BIGNUM * table[][255], int len) // table is len's array of array of 255 bignums
{
if (len <= 0) return;
BN_CTX * ctx = BN_CTX_new ();
BN_MONT_CTX * montCtx = BN_MONT_CTX_new ();
BN_MONT_CTX_set (montCtx, elgp, ctx);
BIGNUM * elggMont = BN_new ();
BN_from_montgomery(elggMont, elgg, montCtx, ctx);
BN_MONT_CTX_set (montCtx, elgp, ctx);
for (int i = 0; i < len; i++)
{
table[i][0] = BN_new ();
if (!i)
BN_from_montgomery (table[0][0], BN_value_one (), montCtx, ctx); // 2^0 = 1
BN_to_montgomery (table[0][0], elgg, montCtx, ctx);
else
BN_mod_mul_montgomery (table[i][0], table[i-1][255], elggMont, montCtx, ctx);
for (int j = 1; j < 256; j++)
BN_mod_mul_montgomery (table[i][0], table[i-1][254], table[i-1][0], montCtx, ctx);
for (int j = 1; j < 255; j++)
{
table[i][j] = BN_new ();
BN_mod_mul_montgomery (table[i][j], table[i][j-1], elggMont, montCtx, ctx);
BN_mod_mul_montgomery (table[i][j], table[i][j-1], table[i][0], montCtx, ctx);
}
}
BN_free (elggMont);
BN_MONT_CTX_free (montCtx);
BN_CTX_free (ctx);
}
BIGNUM * ElggPow (const uint8_t * exp, int len, BIGNUM * table[][255], BN_CTX * ctx)
// exp is in Big Endian
{
if (len <= 0) return nullptr;
BIGNUM * res = nullptr;
BN_MONT_CTX * montCtx = BN_MONT_CTX_new ();
BN_MONT_CTX_set (montCtx, elgp, ctx);
for (int i = 0; i < len; i++)
{
if (res)
{
if (exp[i])
BN_mod_mul_montgomery (res, res, table[len-1-i][exp[i]-1], montCtx, ctx);
}
else if (exp[i])
res = BN_dup (table[len-i-1][exp[i]-1]);
}
if (res)
BN_from_montgomery (res, res, montCtx, ctx);
BN_MONT_CTX_free (montCtx);
return res;
}
BIGNUM * ElggPow (const BIGNUM * exp, BIGNUM * table[][255], BN_CTX * ctx)
{
auto len = BN_num_bytes (exp);
uint8_t * buf = new uint8_t[len];
BN_bn2bin (exp, buf);
auto ret = ElggPow (buf, len, table, ctx);
delete[] buf;
return ret;
}
// DH
DHKeys::DHKeys (): m_IsUpdated (true)